i am guessing that you are asking about Christmas tree ornaments?
as far as most ornaments in the u.s. go most people choose the ball shaped multi-colored ornaments. these are typically the size of a tennis ball, though they can vary greatly from golf ball to a softball size. all colors are used red, blue, green, yellow etc. of course, you can decorate with one color if you like. for example, all red balls on a green tree with white lights. don’t let me dissuade you from choosing an ornament you like. you mentioned icicle shape, that’s fine, stars or homemade ornaments are fine…anything that you like for your tree. there is not really a guideline per-say.
as with anything, prices will vary from around $5 for a box of 12 at a kmart or walmart to $25 plus per ornament for some finer more delicate options (like the blown options you mentioned). just remember, it’s your tree, just have fun and enjoy the holidays. i hope i helped a little. hey, were talking Christmas in july!!